Organo-phosphorus fungicides are now extensively employed mainly for treating rice diseases caused by fungi Piricularia oryzae and Pellicularia sasaki (cf. A. F. Granov, N. N. Melnikov "Uspekhi Khimii", 1973, 42, 9, 1681).
Fungitoxical agents are found among different typs of organo-phosphorus compounds including derivatives of phosphoric and phosphonic acids, phosphines and phosphonium salts, acids of tetracoordination phosphorus and salts thereof, esters of acids of tetracoordination phosphorus, and amides of phosphorus acids.
As a fungicidal thereapeutic compound for treating dermatomycoses known in the art is O,O-dimethyl-1-acetoxy-2,2,2-trichloroethylphosphonate (chloracetophos)--the closest analogue of the novel compounds according to the present invention cf. USSR Inventor's Certificate No. 280768, Bulletin of inventions, 1970, No. 28, p. 93).
Currently known organo-phosphorus fungicides are slightly effective against plant diseases, in particular in killing rust fungi causing most dangerous diseases of cereal and other crops.
For successful control of rust diseases of cereal crops being cultivated in vast areas, highly-effective fungicides are needed that are suitable for efficient application methods, e.g. for the ultra-small volume spraying (USVS) method.
A high activity in respect of rust diseases of cereal crops is revealed by dithiocarbamic acid derivatives, in particular by zinc ethylenebisdithiocarbamate (zineb). These fungicides, however, ar not suitable for application by the USVS method. Besides, these products are not stable upon storage and are harmful to human beings as well as the environment (1. Choinka A., Mosinski S. Pr. Inst.przem. organ., 1971, 3, 269; 2. Ivanova-Chemishanskaja "Gigiena i Sanitaria" 1971, No. 11, 95; 3. E. A. Antonovich et al. "Gigiena i Sanitaria", 1972, No. 9, 25). An essential disadvantage of dithiocarbamate fungicides resides in their limited application, i.e. they are effective only for the purpose of prophylaxis (prior to appearance of visualized symptoms of the disease). For this reason, their application may be effective only upon availability of trustworthy forecasts of disease development.
The above-mentioned disadvantages of dithiocarbamate fungicides gave rise to investigations aiming at finding appropriate substitutes therefor (cf. Gibney L., Chem. and Eng. News, 1975, 53, No. 23, 15).
A high activity against rust diseases is inherent in salts of nickel or mixtures thereof with ethylenebisdithiocarbamic acid derivatives (cf. Jones R. J., E.Afric.Agric. and Forest J., 1961, 26, No. 4, 210; Hardison J. R., Phytopathology, 1963, 53, No. 2, 209). However, due to a detrimental effect of said compounds on human organisms and environments, the use of nickel-containing fungicides has been prohibited (cf. J. Horsefall, Presentation to VIII Congress on Plant Protection, Moscow, 1975).
Ammonium salts of sulphanilic acid such as anilate have been suggested for killing rust fungi of cereal crops and other plants (cf. USSR Inventor's Certificate No. 178236, 1964; Bulletin of inventions, 1966, No. 2, 138). These compounds, however, are phytotoxic and of low-efficiency.
Certain modern system fungicides have proven to be efficient in killing rust fungi, e.g. 1,4-dioxide-2,3-dihydro-6-methyl-5-phenylcarbamoyl-1,4-oxathiine (hydroxycarboxine, plantwax), cf. "Systemic Fungicides", "MIR" Publishing House, 1975, p. 209. However, the use of these fungicides for treating rust diseases of cereal crops is in most cases economically inefficient due to the high cost of the compounds.